Process for producing a shaped detergent body with a high builder content

ABSTRACT

A process for producing a shaped detergent body having a solid component comprising at least 65 wt % of builders, wherein the process comprises injection molding.

The present invention relates to a detergent body containing a highproportion of solid materials. The body is prepared by injectionmoulding.

In applications involving washing agents, detergents and other detergentformulation components, tablets have established a place for themselveson the market in recent years as a format that provides easy meteringand is simple to use.

Tablets typically comprise a mixture of components that are solid atroom temperature and components that are liquid at room temperature.Commonly the solid components are present in granular form for ease ofprocessing and speed of dissolution/dispersion.

The tablets are normally prepared by admixture of the tablet componentsfollowed by compaction to a shaped body. These compressed tablets sufferfrom several disadvantages.

Firstly, even though the compaction pressure used is high the tabletsare still friable. This leads to dust formation and, in some cases,tablet breakage. This problem has not been successfully addressed by theincorporation of binders within the tablet.

Additionally, as the tablet components are usually highly hygroscopic,on exposure to atmospheric air, the tablet absorbs moisture. Withmoisture absorption the tablet deforms and eventually looses itsstructural integrity. To counter this effect a water resistantcontainer/wrapper is required to ensure tablet stability, requiring anadditional step in the manufacturing process.

These and other disadvantages are also relevant for multi-phase tablets,tablets which contain one or more component formulations commonlypresent in a layered arrangement/body with insert formation.

Multi-phase tablets also suffer from complex manufacturing techniques:either a complex multi-stage manufacturing process involving a number oflayers being compressed together (after possible separate pre-formation)and/or the insertion of an insert into cavity of a pre-formed body isrequired.

For the layered structures a compromise has to be reached between asufficiently high compression pressure so that the layers are adequatelybonded together and a sufficiently low compression pressure so thattablet in-wash dissolution/dispersion time is not unduly prolonged. Thiscompromise often has unsatisfactory results leading to tablets havingpoor stability with detrimental effects such as layer separation.

For the tablets having an insert, there is the issue of insert additionwhich requires a highly precise manufacturing process and the problem ofinsert separation caused by poor adhesion to the tablet body.

Detergent tablets may also be prepared using extrusion techniques. Inthis method the tablet components are inserted into an intrusion deviceand extruded.

Tablets produced in this way also suffer from several disadvantages.

Most of the disadvantages arise as a result of the fundamentals of theextrusion process: the extrudate is typically tubular, which is thendivided into tablet portions, usually in a cutting technique. It hasbeen found to be very difficult to cut the extrudate into individualtablets without causing deformation to the tablet. Thus the tabletsproduced are not rectilinear but instead are distorted, especiallyaround the cut edges.

Additionally due to the manner in which the extrudate is produced thereis virtually no flexibility in the shape of the final tablet (with theexception of the shape of the extrusion die): the extruded tablets mustbe based on a kind of tubular form. This problem is particularlyexacerbated for multi-phase tablets.

Also for multi-phase tablets there is a further disadvantage in thatlittle or no flexibility is allowed in the relative proportions in thephases. This problem is described more clearly in Patent ApplicationWO-A-01/02532. Herein a multi-phased tablet (in this case two phases) isdescribed, in which of the two phases the minor phase has to have athickness of at least 5 mm for the integrity of the tablet to bepreserved.

It is an object of the present invention to mitigate/overcome theproblems outlined above.

According to the first aspect of the invention there is provided adetergent body containing a high proportion of a solid component,wherein the detergent body is produced in an injection moulding process.

We have surprisingly found that high solid content compositions can beprocessed in an injection moulding process into a detergent body. Thisis unexpected as normally injection moulding is only considered suitablefor composition predominantly comprised of thermoplastic materials thatmelt/soften (such as waxes) during the injection moulding process. Solidcontaining compositions are not normally processed in this way due tothe detrimental abrasive effect of the solid component. This isparticularly important in a detergent context as many detergentmaterials, such as builders, for example, are typically solid at roomtemperature.

Furthermore, the bodies have been found to have excellent physicalproperties including very smooth/glossy external surfaces and extremelylow friability. Indeed friability has been found to be especially low atthe apexes of the detergent body. Thus the problems exhibited by priorart tablet compositions of dust formation/high friability have beenaddressed.

Generally the detergent body formulation comprises a binder.

The binder is preferably present at 5-50 wt %, more preferably 5-40 wt %and most preferably 10-30 wt % (e.g. such as between 10-20 wt %) of theformulation of the detergent body.

The binder is most preferably a thermo-plastic material. Preferably thebinder comprises a material which is solid at 30° C., most preferably at35° C. Such material has been found to display excellent properties inbody formation and body stability. More specifically the binder has beenfound to have the ability to aid the passage of the detergent bodyformulation into the injection moulding body and also to hold the bodytogether after moulding.

Furthermore, the binder has been found to coat the solid component ofthe detergent body. This is advantageous as with the preferred binders,the previously observed problem of hygroscopicity of the solidcomponents has been reduced. Also as the solid components are coated bythe binder the problem of detrimental interaction of mutuallyincompatible solids (such as enzymes and bleaches) has been vastlyreduced.

Preferred examples of binders include poly-ethylene-glycol (PEG)substituted and non-substituted synthetic and natural waxes (in bothcases water soluble and non-water soluble, sugars and derivativesthereof, gelatine (combined with a sugar and/or a solvent (such as aliquid polyol, e.g. glycerine), non-ionic surfactants such asalkoxylated fatty acids/alcohols; water soluble or water dispersibleoligomers and polymers (both substituted and non-substituted) such aspoly-vinyl-alcohol (PVA), poly-vinyl-pyrrolidone (PVP), cellulose,polycarboxylic acids and co-polymers/derivatives thereof.

Most preferably the binder is PEG. Preferred examples of PEG have amolecular mass of 1500, 6000, 8000, 20000, 35000 or 8 million.

The term solid is to be understood as referring to a material which issolid at the processing temperature (temperature reached during theinjection moulding process). Preferably the solid content of thedetergent body is at least 50 wt %, more preferably at least 65 wt % andmost preferably at least 80 wt %.

Generally the solid component comprises at least 50 wt % builders.

The preferred builder material is of the oligocarboxylate orpolycarboxylate type, such as compounds selected from the groupconsisting of citric acid (and salts, e.g. alkali metal salts thereof),methylglycinediacetic acid (and salts, e.g. alkali metal salts thereof),sodium polyacrylate (and its co-polymers), sodium gluconate and mixturesthereof. Most preferably the builder is an alkali metal (e.g.sodium/potassium) citrate salt.

Optionally the builder material at least partially comprises aphosphorous based builder, such as a tripolyphosphate, e.g. sodiumand/or potassium tripolyphosphate.

The solid component may comprise other conventional solid detergentcomponents such as enzymes (e.g. proteases amylases or lipases),especially when in crystalline/particulate format, bleaches (such aspercarbonate or perborate compounds, chlorine bleach compounds andperacid compounds), bleach activators (such as TAED or metal catalysts)and alkalis (such as hydroxides/carbonates).

Generally the detergent body formulation comprises a lubricant. Such amaterial has been found to display excellent properties in bodyformation. Namely the lubricant has the ability to facilitate thetransport of the detergent body formulation into/within the injectionmoulding mould.

This has a positive effect on the energy required for the requireddetergent body processes. Also it has an effect on reducing the wear ofthe injection mould equipment.

The lubricant is preferably present at 0.1 wt % to 10 wt %, preferablyfrom 0.2 wt % to 5 wt %. It has been found that at such a smallpercentage the effect of the lubricant on the final shape of thedetergent body is minimised.

Preferred examples of lubricants include; fatty acids and derivativesthereof, such as alkali metal and ammonium salts of fatty acidcarboxylates (e.g. ammonium stearate, sodium oleate, potassiumlaureate), also PEG/glycerol functionalised with fatty acid carboxylates(e.g. PEG mono-oleate, PEG ricinoleate, glycerol mono-ricinoleate);sucrose glycerides; oils (olive oil, silicon oil, paraffin oil); and lowmelting point non-ionic surfactants.

The detergent body may have a coating. Where present the coating may beemployed to provide an additional layer of protection to the detergentbody. Additionally/alternatively the coating may be used to attach asecond or further detergent body to the original detergent body.

Where present the coating comprises 0.1 wt % to 5 wt %, preferably from0.2 wt % to 2 wt % of the detergent composition.

Most preferably the coating is dispersible/soluble in water. Preferredexamples of coating materials include fatty acids, alcohols, diols,esters, ethers, mono and di-carboxylic acids, polyvinyl acetates,polyvinyl pyrrolidones, polylactic acids, polyethylene glycols andmixtures thereof.

Preferred mono-carboxylic acids comprise at least 4, more preferably atleast 6, even more preferably at least 8 carbon atoms, most preferablybetween 8 and 13 carbon atoms. Preferred dicarboxylic acids includeadipic acid, suberic acid, azelaic acid, subacic acid, undecanedioicacid, dodecandoic acid, tridecanedioic and mixtures thereof.

Preferred fatty acids are those having a carbon chain length of from C₁₂to C₂₂, most preferably from C₁₈ to C₂₂.

The coating layer may also include a disrupting agent.

The detergent body may further include other common detergent componentssuch as corrosion inhibitors, surfactants, fragrances, anti bacterialagents, preservatives, pigments and dyes.

The detergent body is preferably for use in an automatic washing processin an automatic washing machine. Most preferably the detergent body isfor use in an automatic dishwashing process.

According to a second aspect of the invention there is provided aprocess for producing a detergent body containing a high proportion of asolid component, wherein the process comprises injection moulding.

It will be appreciated that features of the first aspect of theinvention shall apply mutatis mutantis to the second aspect of theinvention.

It has been found that detergent bodies produced using the productionprocess of the second aspect of the invention have excellent propertiesresulting from the injection moulding component.

Firstly, it has been observed that the bodies produced have a highdensity. This is especially beneficial where the body is for use in anautomatic washing machine (particularly a dishwashing machine) asnormally there is only limited space for accommodating the detergentbody. Thus by using the process of the present invention a small densedetergent body may be produced, wherein the said body containssufficient detergent active to achieve its washing requirements yet isable to fit into the space provided in a washing machine.

Additionally as the body is produced by an injection moulding processthere is much greater flexibility over the shape of the body produced.This can be useful if the body has to be accommodated in a specificspace (see the paragraph above). It is also useful from a designfreedom/aesthetic view point; no longer need the detergent body be basedon the limited range of shapes that can be produced by compression orextrusion, any moulded shape can be produced.

Furthermore it has been observed that when bodies are produced byinjection moulding, wherein the bodies comprise a particulate component,there is much greater flexibility of particle size of the particulatecomponent. This is in contrast to particulate bodies produced in acompression process wherein to produce coherent bodies there is usuallyan upper limit on the particle size of around 1500 μm: if the particlesize is any greater the integrity of the body becomes compromised.Whereas in accordance with the process of the present invention bodiescan be produced comprising a particulate component having a particle ofbigger than 1500 μm.

The use of larger particle sizes in the bodies provides severaladvantages in the production process. Primarily the use of largerparticle sizes permits the use of a lower amount of binder with obviouscost saving advantages. Also the problem of pipework/conduit vesselcoating, which is a recognised issue for small particles (especiallywhen used in small quantities) is vastly reduced.

It has also been observed that a broad range of particle sizes can beused in the process according to the present invention. This is incontrast to conventional compression processes wherein there is a needfor a narrow particle size distribution to avoid segregation ofingredients.

A preferred particle size is between 50 μm and 2000 μm with any particlesize distribution within these limits.

These advantages may be realised without incurring any detrimentaleffect on other tablet properties (such as strength, dissolution speed,etc)

The preferred processing method is as follows:

a) Feed the materials to the barrel (hopper) of the injection unit(injection unit is to be understood as being the barrel, the screw andthe nozzle) of the injection moulding machine.

b) Cause the added admixture to be progressed along the barrel of theinjection moulding machine towards the injection nozzle. As theadmixture progresses along the barrel it is mixed and heated above theplastification temperature of the binder.

c) The composition is injected into the mould at temperatures above theplastification temperature.

d) In the mould the composition is allowed to chill.

e) The mould is opened and the shaped body is ejected from the mould.

The process may include one or more of additional steps(f) and/or (g):

f) The body is coated with a coating material.

g) The body is packed (e.g. with foil wrapping, box or bag packing). Thepackaging material may be used to provide a moisture barrier.

In step (a) the component materials may be blended before addition tothe barrel.

In step (a), as an alternative, one of the binder and/or lubricantcomponents may be partially/fully added to the admixture inside thebarrel of the injection unit of the machine by additional feedingstations.

In step (a) the component materials (particularly the binder) are addedto the barrel preferably at a temperature below the plastification ofthe binder system to allow smooth feeding.

As an alternative in step (a) the component materials, optionallyincluding the binder, may be heated above the plastification point ofthe binder and then added to the barrel.

In step (c) the pressure at the nozzle of the injection moulding machinewhile injecting is preferably less than 100 bar, more preferably lessthan 50 bar and most preferably less than 30 bar. Using these relativelylow injection pressures (and consequently low injection temperatures) ithas been found that the integrity (and hence the activity) of any enzymepresent in the injected composition is largely preserved.

In an alternative embodiment the process is performed using an injectionunit which comprises a barrel equipped with a piston to press thedetergent composition into the mould. In this case the detergentcomposition needs to be heated above its plastification temperature andvigorously mixed before being placed in such injection unit. Thedetergent composition can then be injected into the mould.

The process of the present invention may be used in the preparation ofmulti-phase detergent bodies.

For manufacturing a multi phase detergent body the process is mostpreferably performed using a machine which comprises a plurality ofinjection units. Each injection unit is able to process a differentcomposition.

Thus for manufacturing a multi phase detergent body the mould may beconfigured such that it can be accessed by a plurality of injectionunits. Thus a first injection unit may be used to inject a firstcomposition into a first portion of the mould. Simultaneously (orsubsequently) a second injection unit may be used to inject a secondcomposition into a second portion of the mould. Movement of the mouldrelative to one or more of the injection units may occur at a part ofthe process.

As an alternative the mould may be opened after injection and chillingof the composition of the first phase of the detergent body. Theoriginal mould counter part which was moved in order to open the mouldmay be discarded and replaced with a second mould counter part. Themould may then be closed with the second mould counter part leaving avoid space and the composition of the second phase injected therein.

As an further alternative the mould may be arranged such that itcomprises a moveable member which affects the volume within the mould.Most preferably the member may be arranged in at least two orientations:in a first orientation a first volume is defined within the mould and ina second orientation a second (preferably larger) volume is definedwithin the mould. Thus a first composition may be injected into themould with the member in its first orientation. The first injectedcomposition may then be allowed to cool. The member may then be moved toits second orientation, thus realising a void space into which a secondcomposition may be injected.

A yet further alternative is that the mould may be opened afterinjection and chilling of the composition of the first phase of thedetergent body. The first phase of the detergent body may be expelledfrom the mould and inserted into a second mould which after closingcomprises a void space. The composition of the second phase may beinjected into the void space.

For all options above the described process steps may be repeated forthe injection of a third/subsequent composition. A combination of thedifferent alternatives may also be used.

It has been observed in the process according to the invention that itcan be used for the production of multi-phase detergent bodies havingexcellent properties. These properties include much greater flexibilityin the relative arrangement of the phases as the arrangement of thephases in now no longer overruled by gravity and gravity controlled feedtechniques as used in prior art multi-phased tablets produced byconventional compression processes.

Additionally the relative sizes of the phases is much more flexible: anyrelative size of phases is possible, no pre-set relationship is requiredas in extrusion processing prior art.

Furthermore, where a different binder is used in each phase, therelease/dissolution/dispersion properties of each phase can easily becontrolled. The said control has been found to be much more precise asit is no longer influenced by compression pressures; this has been foundto be a particular problem wherein two phase tablets were formed by acompression method with the second phase being compressed on top of thealready compressed first phase. This led to variations in thecompression pressures of the phases and variations in the tablet phasedissolution dispersion rate.

The invention is now described with reference to the followingnon-limiting examples.

EXAMPLES

Formulation Preparation

Several Formulations were prepared in accordance with the followingtable.

In each case tablets of 20 g were produced. The tablets were rectangularin shape (26 mm×36 mm×14 mm) with a small indentation on one of thelargest faces (suitable for insertion of a second detergent compositioncomponent).

Formulation Components % 1 2 3 4 5 6 7 8 9 STPP 24 24 24 24 24 32 3237.6 — Sodium-Citrate 48.25 48.25 48.25 48.25 53.25 17.6 17.6 — 49Protease, speckles 0.75 0.75 0.75 0.75 0.75 — — 0.6 1.5 Amylase,speckles 0.5 0.5 0.5 0.5 0.5 — — 0.4 0.5 Sulphonated Polymer 5 5 5 5 5 —— — 5 Nonionic Surfactant 1.5 1.5 1.5 1.5 1.5 1.2 1.2 1.2 1 PEG M_(w) =20000 g/mol 20 20 15 15 10 — — — — Copolymer PVP-VA — — 5 5 5 — — — 2Sodium Disilicate — — — — — 2.8 2.8 2.8 1 Soda Ash — — — — — 23.2 23.223.2 8 PA Homo-polymer — — — — — 3.2 3.2 1.2 5 PEG M_(w) = 6000 g/mol —— — — — 20 — 20 12 Fatty Acid Alcohol 25 EO — — — — — — 20 — 5 SodiumPercarbonate — — — — — — — 9.6 — TAED — — — — — — — 3.2 — SodiumPhosphonate — — — — — — — 0.04 — Silver Corrosion inhibitor — — — — — —— 0.2 — Methyylglycinediacetic - — — — — — — — — 10 acid saltGranulation R F R F R R R R R Formation Temperature (° C.) 100 100 100100 100 70 70 70 60 Formation Pressure (bar) 500 500 500 500 600 250 250250 50 Definition of fine and rough granulation: R = Rough Granulation:200 to 1200 μm particle size (70% of granules are in the range of 400 μmto 1000 μm). F = Fine Granulation: 0-600 μm particle size (70% ofgranules are in the range of 50 μm to 300 μm)Formulation Dissolution Measurement

Each Formulation was tested to measure its dissolution time.

Two different dissolution tests were used as below.

Test #1

A Bauknecht Avanti GSF dishwasher is filled with 4 L of water and heatedup to 50° C.

The injection moulded Body is placed on the bottom of the dishwasher andallowed to dissolve. The spray arm is used to distribute the water as ina normal wash cycle.

The dissolution is measured by measuring conductivity of the watermedium. When the conductivity value stays constant and does not increaseany further it is assumed that the injection moulded Body has completelydissolved. This point is taken as the dissolution time. The measurementis repeated 3 times and the average value is calculated.

This test was carried out on Formulations 1 to 5 and the results areshown in Table 1.

TABLE 1 Formulation 1 2 3 4 5 Dissolution Time (min) 22 23 42 40 50Test #2

A 1 L beaker is filled with 800 mL of tap water. The water is heated to40° C. and maintained at that temperature with a coil immersion heaterhaving an associated contact thermometer.

With a standard pharmaceutical disintegration tester (Erweka brand) withup-and-down moving sieves the shaped bodies are moved up-and-down in thewater. The point of complete dissolution is defined as the point whenthe whole shaped body is dissolved/disintegrated from the basket.

This test was carried out on Formulations 6 to 8 and the results areshown in Table 2.

TABLE 2 Formulation 6 7 8 Dissolution Time (min) 20 45 21

SUMMARY

General:

Powder Formulations with rough and fine granulation can be injectionmoulded into tablet shapes, (see particularly Formulation 1 andFormulation 2).

All shaped bodies had very smooth surfaces and a glossy appearance. Thebodies all showed low dusting and very low friability.

The dissolution times of these Formulations (especially Formulations 1,2 and 6) are very short and are similar to release profiles of currentdishwasher tablets commercially available.

Granulometry:

Formulation 1 and Formulation 2 compare the use of different granulesizes in the process.

Surprisingly both granulometries can be used exchangeable yet producetablets having very similar properties: the change in granulometry wasshown to have no effect on the dissolution characteristics of the tabletproducts. Also there were no differences in the ease with which thetablets could be processed: the injection moulding process wasunaffected by a change in particle granulometry. This is surprising andis in contrast to conventional compressed particulate tablets where theparticle granulometry has a huge effect on tablet dissolution time.

Binder:

A binder content of 15 wt % is sufficient for a smooth injectionmoulding processing operation. The operation has been shown to bepossible with a wide range of different binders.

We have shown that by modifying the binder system different dissolutionspeeds can be altered. This can be used to make multi phase productsdisplaying sequential dissolution.

This effect may be illustrated with reference to Formulations 1 and 3.These Formulations have almost the same composition and are made in thesame way. The difference between the Formulations is that in Formulation1 the binder is PEG (M_(w)=20000 present at 20 wt % of the Formulation)whereas in Formulation 3 the binder comprises 15 wt % PEG M_(w)=20000and 5% polypyrrolidone-polyvinylacetate copolymer (PVP-VA). Thedissolution times of Formulation 3 is twice that of Formulation 1.

A similar comparison can be made between Formulations 2 and 4 and alsobetween Formulations 6 and 7.

Stability of Ingredients:

Formulation 3 was tested directly after processing. It was found thatthe enzymes in the formulation (amylase, protease) were each at 50% oftheir original activity level.

Formulation 9 was tested directly after processing. It was found thatthe enzymes in the formulation (amylase, protease) were each at 100% oftheir original activity level.

Further studies were undertaken to show the impact of injection mouldingpressure/temperature on enzyme stability on Formulation 9. The resultsof these studies are shown in Tables 3 & 4.

TABLE 3 Injection Pressure (bar) 400 200 100 50 30 % age Enzyme Activity20 40 90 100 100 after Processing

TABLE 4 Injection Temperature (° C.) 100 90 70 60 % age Enzyme Activityafter Processing 20 40 90 100

Formulation 8 was stored at 30° C./70% rH and was analytically checkedafter 6 weeks.

After 6 weeks it was found that Formulation 8 still had from 90 to 100%of the starting material of TAED, BTA and percarbonate. This is morethan typically obtained in storage tests of corresponding tabletproducts made by compression.

1. A process for producing a detergent body having a solid componentcomprising at least 65 wt % of a builder selected from the groupconsisting of oligocarboxylate compounds, polycarboxylate compounds,phosphorus based builder, and mixtures thereof, comprising the followingsteps: a) feeding component materials comprising the builder and abinder for producing a composition to a barrel or hopper of an injectionunit of an injection molding machine; b) causing the component materialsto be progressed along the barrel of the injection molding machinetowards an injection nozzle; c) injecting the component materials into amold at a temperature above the plastification temperature of thebinder; d) allowing the composition to chill in the mold; and e) openingthe mold and ejecting a shaped body therefrom.
 2. A process according toclaim 1, wherein the builder is an alkali metal citrate salt.
 3. Aprocess according to claim 1, wherein the binder comprises from 5 to 30wt % of the detergent body.
 4. A process according to claim 3, whereinthe binder comprises from 5 to 20 wt % of the detergent body.
 5. Aprocess according to claim 3, wherein the binder comprises athermoplastic material having a melting point of about 35° C.
 6. Aprocess according to claim 3, wherein the binder is polyethylene glycolhaving a molecular mass of between 1,500 to 35,000.
 7. A processaccording to claim 1, wherein the process comprises adding a lubricantas a component material.
 8. A process according to claim 7, wherein thelubricant comprises from 0.1 to 10 wt %.
 9. A process according to claim1, wherein the shaped body is coated with a coating material.
 10. Aprocess according to claim 1, wherein the shaped body is packed with apackaging material.
 11. A process according to claim 1, wherein thecomponent materials are blended before addition to the barrel.
 12. Aprocess according to claim 1, wherein the binder or at least onelubricant component is at least partially added to the admixture insidethe barrel of the injection unit of the injection molding machine byadditional feeding stations.
 13. A process according to claim 1, whereinin step (a) the component materials are added to the barrel at atemperature below the plastification temperature of the binder.
 14. Aprocess according to claim 1, wherein in step (a) the componentmaterials are added to the barrel at a temperature above theplastification temperature of the binder.
 15. A process according toclaim 1, wherein in step (c) a pressure at the nozzle of the injectionmolding machine while injecting is higher than 50 bar.
 16. A processaccording to claim 1, wherein the process is performed using a machinewhich comprises a plurality of injection units with each injection unitable to process a different composition.
 17. A process for preparingmulti-phase detergent bodies according to claim 1.